Web winding apparatus

ABSTRACT

A web-winding system is disclosed as employing clutches so ganged on a common drive that wide webs may be wound simultaneously with, and to the same tightness as, narrower webs. The coupling of each such clutch is controlled by a computer which operates by maintaining constant the total end face area of the supply and rewind rolls. The drive speed is also computercontrolled to minimize the heat-producing slippage within such clutches.

nitdl tates Met 2,684,210 7/1954 Conti lnventor Thomas 1 1. OrmsbyMoclzmter, NY.

June 2, 11969 Sept. 7, 19711 Eastman Medals Company liter-heater, NY.

Appl. No. lFiled Patented Assignee ill/1111B WMWIDHNG APPARATUS 1111 (Id Mir-awning Figs.

111.5. (III.

int. Cl. B6511 35/02 ll leldl all 1111 Retell-renew Qi'ted UNITED STATESPATENTS 3,010,671 11/1961 Brown 242/569 3,214,110 10/1965 Ross 242/755 X3,348,107 10/1967 l-lamby. 242/7551 X 3,373,332 3/1968 Olsen 242/7551 X3,411,055 11/1968 Carter etal 242/75.51 X 3,424,395 1/1969 Schmidt etal.242/569 X Primary Examiner-Stanley N. Gilreath Assistant Examiner-Werner1-1. Schroeder Attorneys-Walter O. Hodsdon and Robert F. Cody ABSTRACT:A web-winding system is disclosed as employing clutches so ganged on acommon drive that wide webs may be wound simultaneously with, and to thesame tightness as, narrower webs. The coupling of each such clutch iscontrolled by a computer which operates by maintaining constant thetotal end face area of the supply and rewind rolls. The drive speed isalso computer-controlled to minimize the heat producing slippage withinsuch clutches.

PATENTED SEP "H971 $HEET 32 OF H THOMAS fl. ORMSBV INVENTOR.

A TTOR/VEYS PATENTED SEP (19?! SHEET 0F 2 RBI THOMAS H. ORMSBY INVENTOR.

IM T (w IN T CM S A TTOR/VEYS WlEH Wlll lDllN G AlPlPAiRAT US BACKGROUNDUP THE INVENTZON ll. Field Of'lhe invention This invention relates ingeneral to web-handling equipment. While one aspect of the invention isdirected to the simultaneous winding of plural webs,to the same rolltightness, other aspects of the invention may find usefulness incontrolling the winding ofany number of webs.

Description Relative To The Prior Art in the field of web winding, it iswell known to increase the torque of winding apparatus as the radius ofthe web roll in question increases, thereby to control the tightness ofsuch roll. U.S. PAT. No, 2,684,210 particularly points out how thistechnique may be implemented by use of a slip clutch, the coupling ofwhich is adjusted in relation to roll radius. U.S. PAT. No. 2,684,210further suggests that the drive input speed of the clutch may be reducedas the radial dimension of the roll increases, thereby to decreaseslippage within the clutch, and thus prolong clutch-life. U.S. PAT. No.2,796,222 similarly indicates, in web-handling apparatus, the control ofclutch coupling and input speed; and particularly indicates how theproblem of disposing of heat generated by overdriving the input of theclutch may be avoided by directly measuring clutch slippage, andemploying a signal representing such slip page for purposes of clutchinput speed control.

Where plural webs of different widths are to be wound simultaneously bythe same drive, a problem presents itself if all such webs are to bewound to the same tightness: Winding two rolls of the same instantaneousradius, but of different axial dimensions, requires more torque for thewider roll than for the narrower one. if winding is governed by thetorque requirements of the narrower roll, the wider roll will be tooloosely wound; if winding is governed by the torque require ments of thewider roll, the narrower roll may cinch under its own tightness. Suchmanifestations are especially bothersome when winding photographic webs,viz because they tend to degrade optically the surfaces of such websand/or their coatings,

In determining torque requirements as a function of the radial dimensionof a web roll, it is frequently desirable to do so without actuallydetecting/measuring, e.g. by means of a feeler in contact with the roll,the radius of such roll. And, as will appear below, meeting the torquerequirements of apparatus adapted to wind plural webs of differentwidths augmerits the need for controlling clutch input speed, especiallywhere thermally nonconductive photographic webs are to be wound. As inthe case of torque control without use of roll feelers, etc, it is oftendesirable also to control the input speed of a clutch without resort tofeedback devices on, or associated with, the roll being wound.

SUMMARY OF THE llNVENTiON The invention is indicated in the environmentof a system for slitting a wide web, say of photographic film, which hasbeen peeled from a supply roll thereof, into any number of narrower webs(hereinafter sometimes referred to as rewindwebs) of the same ordifferent widths; and then simultaneously winding all such narrower websinto respective rolls thereof. Such a system illustrates the variousproblems solved by, and features of, the invention:

To meet the torque requirements of web rolls as functions both of theirradii and widths, the invention proposes l, the

use of plural clutches on a common drive shaft -which clutches are soganged that wider rewind-web rolls are driven by more clutches thannarrower rewindweb rolls and 2 the respective coupling of each suchclutch in accordance with roll radius, To facilitate such gauging ofclutches, the clutches are preferably alike", their respective outputmembers being so dimensionally larger radially (concentrically) thantheir input members that-web winding necessarily occurs on and about oneor more of such output members. Thus, web slitting may occur anywhere,and any number of times, across the width ofa wide web, the clutchescooperating in groups to provide wind up torque commensurate with thewidths of the respective webs being rewound.

Winding thermally nonconductive (photographic) webs on and aboutclutches, in the manner indicated above, requires that heat-producingslippage within such clutches be kept to a minimum. Apparatus accordingto the present invention not only controls the input speed ofaclutchthereby to minimize its slippage-without sensing rewind-webparameters, but also controls the torque of such clutch as a function ofthe radius of its respective rewind roll, without actually detecting/measuring the radial dimension of such roll. Such speed and torquecontrols are made possible by a computer which operates on the followingpremise: The total end face area of web supply and rewind rolls will beconstant provided the tightness of the supply roll is the same as thetightness of the rewind roll; and such tightnesses will be the sameprovided the web tension between the rolls is kept constant. Based onsuch premise, the computer provides a signal representing theinstantaneous radius of the rewind roll; and by which signaltension'influencing clutch coupling is controlled. Since web-speed isthe same for both the supply and rewind rolls, the rotational speed ofthe rewind roll can be determined from the instantaneous radii of thesupply and rewind rolls, and the angular speed of the supply roll. Therewind roll speed is the output speed of the clutch in question; and theinput speed to such clutch may be so selected that the clutch slip-speedcan be thermally tolerated.

As will be indicated below, and as presently preferred, the total endface area constant is determined without actually measuring such area.

An object of the invention is to provide a way simultaneously to windinto rolls, and by the same drive, webs of different widths; and whichrolls will be wound to substantially the same tightness as each other,and throughout.

Another object of the invention is to provide, in a system for rewindinga web peeled from a supply roll thereof, apparatus for regulating rewindtorque in accordance with a dimension of the rewind roll, and whichdimension is determined from data derived from the supply roll.

Another object of the invention is to provide an input-speed control fora clutch employed for rewinding a web peeled from a supply roll, thecoupling of which clutch is adjusted in accordance with a dimension ofthe rewind roll, and which speed control obviates the need for feedbackdevices on or as sociated with the rewind roll.

Another object of the invention is to provide speed and/or torquecontrols for a clutch employed for rewinding a web peeled from a supplyroll thereof, which controls are based on the total area of the endfaces of the supply and rewind rolls being maintained constant.

Another object of the invention is to provide a way for determining thetotal end face area of supply and rewind rolls without actuallymeasuring such area.

Another object of the invention is to provide rewind apparatus embodyingany or all of the above-indicated features.

The invention will be described with reference to the figures whereinFlG. l is a perspective view of a system especially adapted toincorporate the various features of the invention,

FIG. 2 is a side elevational view, partially in section, of a clutchuseful for practicing the invention,

FIG. 3 is a block diagram indicating a web winding system according tothe invention, and

FIG. 4 illustrates, in block form, a presently preferred web windingsystem according to the invention, and embodying its various features.

Referring to H6. l, a web it) is peeled from a supply roll 12 thereof,and conveyed past slitters 1 2-. While there is no spe cial form ofslitter ll-ti necessary to practice the invention, it is a feature ofthe invention to accommodate web slitting anywhere, and any number oftimes, across the width of the web 10. For this purpose, the slitters I4are cutting wheels positionably mounted on and driven by a shaft 16.Alternate narrow webs 18, 20, 22, 24, 26, which may be of any selectedwidth, and which are formed by the slitting operation, are wound byrespective drives 28, 30. The drive 28 comprises a motor 32 for drivinga shaft 34 to which a plurality of clutches 36 are ganged; the drive 30comprises a motor 38 for driving a shaft 40 to which a plurality ofclutches 42 are ganged.

A clutch of the type indicated in FIG. 2 has been found especiallyuseful for practicing the invention: The input member 44 of the clutch36 is provided with a keyway 46; and which keyway 46 cooperates with akey 48 on the drive shaft 34 to lock the shaft 34 and clutch inputmember 44 rotationally together. A setscrew 50, accessible through ahole 52 in the clutch output member 54, keeps the clutch from slidinglengthwise of the shaft 34. An electromagnet 56, forming part of theclutch input member 44, receives electrical coupling control signals(via busses 57 disposed on and along the shaft 34) for coupling theclutch input and output members together. The output member 54 of theclutch may be of magnetic material; and such output member has afriction ring 58 for bearing the brunt of the clutch coupling forces.The electrical coupling control signals are provided by a control device60 which increases the electrical power applied to the electromagnet 56as the torque requirements of the clutch increase, i.e., as the rewindroll(s) grows in radius; and a speed control device 62 operates todecrease gradually the speed of the drive shaft 34 as the rewind roll(s)grows in radius, thereby to cut slippage within the clutch(es) 36 andprevent its (their) overheating,

By the above-described apparatus, a web may be slit anywhere, and anynumber of times, across its width, the rewind apparatus always providingthe requisite torque (regardless of web width or roll radius) forproducing rewind rolls all of the same tightness: A narrow rewind webe.g. web 18) which is half as wide as another (e.g. web is wound on, andby, half as many clutches as the wider rewind web; but since the rewindrolls in questions similarly grow in radius, their respective clutchcouplings are similarly simultaneously increased.

FIG. 3 indicates the general scheme of a computer for providing speedand coupling controls without feelers, feedback devices, etc. Componentsfor preforming the various computer functions are well known; and suchcomponents may take any of a variety of forms, as indicated, forexample, in Electric Analog Computers", Korn and Korn, McGraw HillPublishing Company, Inc., 1952.

It should be borne in mind that in the description which follows, thevarious parameters, and signals corresponding therewith, arerespectively similarly designated.

As indicated above, the total area of the end faces 64, 66 of supply andrewind rolls 68, 70 will be constant k provided the respectivetightnesses of such rolls are the same; and such tightnesses will besubstantially the same if the tension in the web 72 between such rollsis kept constant. Web tension may be so maintained by controlling theroll 66 torque as a direct function of the instantaneous radius r of theroll face 66; and such radius may be determined from the instantaneousradius r of the roll face 64 provided the area constant k is known: Thearea constant is the area of the end face 64 at the start of the windingoperation (plus the core area of the rewind roll 70).

The instantaneous radius r of the supply roll 68 is determined asfollows: A tachometer 74 is driven by the supply roll 68, and provides asignal n, representing the rate of rotation of the roll 68. A roller 76having a radius p is driven by the web 72; and such roller 76 rotates ata rate dependent upon the lineal speed of the web 72. The roller 76drives the input of a tachometer 78, thereby to produce a signal n,representing the rotational rate of the roller 76. A signal multiplier(e.g. a patentiometer excited by a voltage representing the roll radiusp and having its wiper positioned in proportion to the signal n,,)

produces the product signal V. The signals V and nrepresentingrespectively the lineal speed of the web 72 as it peels fromthe roll 68, and the angular speed of the roll 68 are divided by and ina divider 82 to produce the quotient signal r, representing theinstantaneous radius of the roll 68.

Based on the above-mentioned premise, a signal r representing theinstantaneous roll (70) radius which is necessary to keep web (72)tension constant is generated by a computer 84 adapted to solve theequation 1Tr +1rr =k for r which signal r; is applied to vary the torqueproducing coupling of a clutch 88 to hold web tension constant. Thus,the rewind torque is controlled in proportion to the radius of therewind rollwithout ever actually measuring/detecting such radius.

As the rewind roll 70 rotates to draw web 72 from the supply roll 68,the rotational rates of the two rolls are tied to each other by theexpression n r =n r and since signals m, r, and r are available withinthe computer 84, the requisite speed n for the roll 70 may bedetermined. The roll 70 speed signal n is combined, in a summing device89 with an overdrive bias signal K, the resultant of which is applied(through an appropriate power control to a motor 90 for driving theinput member of the clutch 88. Thus, the slip speed of the clutch 88(i.e. the difference between its input and output speeds) is held to aconstant represented by the signal K; and the signal K is so chosen(e.g. depending on the thermal characteristics of the web being wound onand about the clutch 88) that heat generated within the clutch 88 can beeffectively dissipated.

The signal K is necessary to convert the system of FIG. 3 from a staticsystem into a dynamic one.

Reference should now be had to FIG. 4 which indicates a presentlypreferred form of computer for practicing the invention; and FIG. 4 alsoillustrates how a good approximation of the total end face area forsupply and rewind rolls may be determined without actually measuringsuch area. Elements having corresponding parts in FIG. 3 arerespectively similarly designated in FIG. 4; but are primed in FIG. 4-.

The supply and rewind roll 68' and 70 are provided with cores 92, 94.The roller 76' is disposed to assist in stripping web 72' from the roll68; and the roller 76 is driven by a motor 96 against the action of abrake 95. After providing a signal r representing the instantaneousradius of the supply roll 68-in the manner of the system of FIG. 3 thesignal r, is multiplied by itselfin a multiplier 100 to produce thesignal r The signal n is algebraically summed, in a device 102, with asignal representing the total area constant k divided by 11' to producea signal r and thereafter a square root device 104 converts the signal rto a signal r representing the instantaneous radius of the rewind roll70. (The manner in which the total area constant-divided by 1risproduced will be discussed later.) The signal r is then applied tocontrol the torque producing coupling of the clutch 88', thereby thekeep constant the tension of the web 72.

The signal V(=r n,) produced by the multiplier is applied to a divider110, wherein such signal is divided by the signal r to produce thesignal n representing that speed for the rewind motor which is necessaryif heat-producing clutch slippage is to be kept to an amount representedby the overdrive signal K.

The total end face area constant k is determined without actuallymeasuring same as follows: At the start of the rewind operation-Le. whenpower is first applied to the system of FIG. 4, by closing gangedswitches 120, l22-the roller 76 starts to peel web 72 from the roll 68':Thus the signal r, is immediately available; and since the core 94radius is a constant R an algebraic summation device 124 immediatelyproduces the signal k/rr. The output signal of the device 124 is,however, only transiently a true representation of the total end facearea (divided by 11'). This is because the supply roll radius r,gradually changes as the supply roll decreases in size; and as the sizeof the rewind roll increases. Accordingly, an AND gate 128 is employedto gate the initial area signal k/rrinto a lhbf d liill storage devicelllltl (eg. a motor llJll7-potentiometer 12,9 combination); and suchgate circuit 112% is turned on by means of a one-shot circuit 113.2which holds the gate lllil open for just enough time (after the switch112?; is closed) to permit a meaningfully representative area signal tobe produced and stored.

During the time when the area signal It/rriS being memorized, the speedcontrol portion of the H0. l system is disabled, thereby to prevent itshunting a continuously changing reference speed. This is effected byinhibiting (inverter Ml), AND gate M2) the application of the roll '70speed signal :1 to the drive 94). Rewind speed is a function of theoverdrive signal l4 during this interval.

The invention has been described in detail with particular reference topreferred embodiments thereof, but it will be understood that variationsand modifications can be effected within the spirit and scope of theinvention. For example, it would be within the scope of the. inventionto attenuate, gradually and slightly, the computed signal r so thatouter roll layers are slightly less tightly wound then inner layers.

1 claim:

l. Apparatus for winding a web of any given width to a prescribed rolltightness; or for simultaneously winding a plurality of webs havingrespective widths, and which apparatus winds said plural webs all to thesame prescribed roll tightness, comprising:

a. shaft means and a drive therefor,

b. a plurality of slip clutches each of which has input and outputmembers and means for varying the coupling there between, said clutchesbeing so mounted on said shaft means that the respective input membersof said clutches are all rotationally driven by said shaft means, theoutput member of each said clutch being dimensionally larger radiallythan its corresponding input member, the radial dimensions of saidoutput members being alike, and said clutches being further so disposedon said shaft that respective tandem combinations thereof may wind abouttheir respective output members webs of respective widths,

. signal responsive means cooperative with the variable coupling meansof said clutches for simultaneously adjusting the respective couplingsof said clutches, and

d. means for producing and applying a signal proportional to the radiusof a roll being wound by said apparatus to said signal responsive means,thereby to control the said couplings in accordance with said signal.

2. The apparatus of claim 1 including means for decreasing the speed ofsaid drive in proportion to the radius of a roll being wound.

3. in a web handling system for slitting a supply web roll into aplurality of narrower rewind webs of respective widths, and forrewinding said narrower webs into rolls thereof, said rolls havingrespective end face areas, and which system has:

a. a rewind shaft, and

b. means for driving said shaft the improvement which comprises aplurality of similarly sized slip clutches having respective input andoutput members, and variable coupling means therebetween, said clutchesbeing mounted on said rewind shaft, means for coupling the respectiveinput members of said clutches to said rewind shaft for simultaneousrotation of said input members by said shaft, the output members of saidclutches being dimensionally alike and larger radially than theircorresponding input members, whereby wider rewind webs are wound on moreclutches than narrower rewind webs.

4. The system of claim 3 including means cooperative with said variablecoupling means for increasing the coupling of said clutches inproportion to the radii of the rewind rolls being wound.

5. The system of claim t including means cooperative with said means fordriving said shaft for decreasing the speed of said shaft in proportionto the radii of the rewind rolls being wound. I 4

b. The system of claim wherein said means for increasing clutch couplingcomprises computer means cooperative with the end face areas of thesupply roll and a rewind roll for producing a control signalrepresentative of the difference between a constant area and the totalend face area of said supply roll and said rewind roll, and means forapplying said control signal to said variable coupling means.

'7. The system of claim 6 including means for continuously producing asignal representing the instantaneous radius of said supply roll, andwherein said computer means is adapted to produce a signal representingthe instantaneous radius of a rewind roll which is necessary to maintainconstant the said end face area, said last named signal being applied tocontrol the coupling said clutches.

b. The system ofclaim 7 including:

a. means for producing and applying a signal representing the angularrate of rotation of said supply roll to said computer means, saidcomputer means being further adapted to produce a signal representingthe angular speed of said rewind shaft which is necessary to maintainconstant the lineal travel of said web from its supply roll to itsrewind roll,

b. means for producing a signal representing an overdrive constant, and

c. means for algebraically combining said rewind speed signal and saidconstant signal into a resultant signal, and for applying said resultantsignal to said means for driving said shaft.

El. The system of claim 7 including a. means independent of said driveshaft for stripping web from said supply roll thereof, and

b. means for producing and storing a reference signal 1. means forproducing a signal representing the lineal speed ofsaid web as it isstripped from said supply roll,

2. means for producing at that time a signal representing the angularrate of rotation of said supply roll,

3. means for defining a predetermined short duration at or'near thestart of said web stripping, which duration occurs before said rewindroll grows appreciably,

4-. means for producing a signal representing the quotient of saidlineal speed divided by said angular speed, and

5. means cooperative with said last-named means during saidpredetermined duration for storing thereafter a signal proportional tothe square of said quotient signal.

ill In a system for peeling a web offa supply roll thereof and rewindingsame into another roll, said rolls having respective end face areas, andwhich system comprises:

a. slip clutch means having input and output members and means forvarying the coupling of said input and output members,

b. means for driving the input member of said clutch, the output memberof said clutch being coupled to drive said rewind roll, the improvementcomprising computer means cooperative with the end face areas of thesupply roll and a rewind roll for producing a control signalrepresentative of the difference between a constant area and the totalend face area of said supply and rewind rolls, and means for applyingsaid control signal to said means for varying the coupling said clutchmeans.

ll. The system of claim ill wherein said computer means includes meansfor producing a signal representing that angular speed for said rewindroll which is necessary to maintain constant the lineal speed of saidweb as it is rewound, and wherein said system includes a. means forproducing a reference signal,

b. means for algebraically combining said speed and reference signalsinto a resultant signal, and

c. means for applying said resultant signal to said means for drivingthe said clutch input member in response thereto.

27 3 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION patent3,603,521 Dated September 7 1971 Inventor(s) Thomas R. Ormsby It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

Column 5, line 47, insert "clutch" before couplings Column 6, line 34,Claim 9 (b), after 'signal" the following line should be insertedproportional to the end face area constant comprising Column 6, line 61,after "coupling insert of Signed and sealed this 9th day of January1973..

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissionerof Patents

1. Apparatus for winding a web of any given width to a prescribed rolltightness; or for simultaneously winding a plurality of webs havingrespective widths, and which apparatus winds said plural webs all to thesame prescribed roll tightness, comprising: a. shaft means and a drivetherefor, b. a plurality of slip clutches each of which has input andoutput members and means for varying the coupling there Between, saidclutches being so mounted on said shaft means that the respective inputmembers of said clutches are all rotationally driven by said shaftmeans, the output member of each said clutch being dimensionally largerradially than its corresponding input member, the radial dimensions ofsaid output members being alike, and said clutches being further sodisposed on said shaft that respective tandem combinations thereof maywind about their respective output members webs of respective widths, c.signal responsive means cooperative with the variable coupling means ofsaid clutches for simultaneously adjusting the respective couplings ofsaid clutches, and d. means for producing and applying a signalproportional to the radius of a roll being wound by said apparatus tosaid signal responsive means, thereby to control the said couplings inaccordance with said signal.
 2. The apparatus of claim 1 including meansfor decreasing the speed of said drive in proportion to the radius of aroll being wound.
 2. means for producing at that time a signalrepresenting the angular rate of rotation of said supply roll,
 3. meansfor defining a predetermined short duration at or near the start of saidweb stripping, which duration occurs before said rewind roll growsappreciably,
 3. In a web handling system for slitting a supply web rollinto a plurality of narrower rewind webs of respective widths, and forrewinding said narrower webs into rolls thereof, said rolls havingrespective end face areas, and which system has: a. a rewind shaft, andb. means for driving said shaft the improvement which comprises aplurality of similarly sized slip clutches having respective input andoutput members, and variable coupling means therebetween, said clutchesbeing mounted on said rewind shaft, means for coupling the respectiveinput members of said clutches to said rewind shaft for simultaneousrotation of said input members by said shaft, the output members of saidclutches being dimensionally alike and larger radially than theircorresponding input members, whereby wider rewind webs are wound on moreclutches than narrower rewind webs.
 4. The system of claim 3 includingmeans cooperative with said variable coupling means for increasing thecoupling of said clutches in proportion to the radii of the rewind rollsbeing wound.
 4. means for producing a signal representing the quotientof said lineal speed divided by said angular speed, and
 5. meanscooperative with said last-named means during said predeterminedduration for storing thereafter a signal proportional to the square ofsaid quotient signal. 10 In a system for peeling a web off a supply rollthereof and rewinding same into another roll, said rolls havingrespective end face areas, and which system comprises: a. slip clutchmeans having input and output members and means for varying the couplingof said input and output members, b. means for driving the input memberof said clutch, the output member of said clutch being coupled to drivesaid rewind roll, the improvement comprising computer means cooperativewith the end face areas of the supply roll and a rewind roll forproducing a control signal representative of the difference between aconstant area and the total end face area of said supply and rewindrolls, and means for applying said control signal to said means forvarying the coupling said clutch means.
 5. The system of claim 4including means cooperative with said means for driving said shaft fordecreasing the speed of said shaft in proportion to the radii of therewind rolls being wound.
 6. The system of claim 4 wherein said meansfor increasing clutch coupling comprises computer means cooperative withthe end face areas of the supply roll and a rewind roll for producing acontrol signal representative of the difference between a constant areaand the total end face area of said supply roll and said rewind roll,and means for applying said control signal to said variable couplingmeans.
 7. The system of claim 6 including means for continuouslyproducing a signal representing the instantaneous radius of said supplyroll, and wherein said computer means is adapted to produce a signalrepresenting the instantaneous radius of a rewind roll which isnecessary to maintain constant the said end face area, said last namedsignal being applied to control the coupling said clutches.
 8. Thesystem of claim 7 including: a. means for producing and applying asignal representing the angular rate of rotation of said supply roll tosaid computer means, said computer means being further adapted toproduce a signal representing the angular speed of said rewind shaftwhich is necessary to maintain constant the lineal travel of said webfrom its supply roll to its rewind roll, b. means for producing a signalrepresenting an overdrive constant, and c. means for algebraicallycombining said rewind speed signal and said constant signal into aresultant signal, and for applying said resultant signal to said meansfor driving said shaft.
 9. The system of claim 7 including a. meansindependent of said drive shaft for stripping web from said supply rollthereof, and b. means for producing and storing a reference signal 11.The system of claim 10 wherein said computer means includes means forproducing a signal representing that angular speed for said rewind rollwhich is necessary to maintain constant the lineal speed of said web asit is rewound, and wherein said system includes a. means for producing areference signal, b. means for algebraically combining said speed andreference signals into a resultant signal, and c. means for applyingsaid resultant signal to said means for driving the said clutch inputmember in response thereto.